Year % 1990 37.82045 1993 40.52888 1995 45.89021 1996 41.86542 1997 37.62429 1998 35.53408 1999 37.07483 2000 36.9614 2001 38.52436 2002 36.87175 2003 37.91603 2004 37.40918 2005 40.57053 2006 37.70107 2007 33.10455 2008 30.95702 2009 31.19703 2010 28.09994 2011 31.34241 2012 32.42157 2013 29.14916 2014 30.17323 2015 29.56101 2016 32.28555 2017 31.52004 2018 30.34628 2019 29.46581 2020 31.17542 2021 31.17267